The burning rates of solid propellant compositions have been the subject of much research and development works. These research and development works have demonstrated in the field of solid propellants that the burning rates of solid propellant compositions are higher as the particle size of the oxidizer is decreased, especially for the ammonium perchlorate oxidizer systems. This relationship of burning rate to particle size of oxidizer has been demonstrated in all of the binder systems used (double base, polyurethanes, polyesters, rubbers, etc.).
Burning rates of solid propellants have also been increased by incorporating metal staples and/or metal flakes as fuel and burning rate promoters. The fabrication of staples in the form of multi-dimensional crosses is a development to achieve metal staples orientation perpendicular to the burning surface since a certain percentage of the staples would achieve random alignment of staples perpendicular to the burning surface (See U.S. Pat. No. 3,389,025, issued to J. E. Nix et al. on June 18, 1968).
Another approach for staple alignment is disclosed in my U.S. Pat. No. 3,598,668, issued on Aug. 10, 1971. The staples disclosed in this patent are of a composite structure consisting of layers of a propellant fuel metal selected from the propellant fuel metals consisting of aluminum, magnesium, zirconium, boron, and alloys containing major portions thereof and a ferromagnetic metal selected from the group consisting of iron, nickel, cobalt and alloys thereof. These staples are aligned perpendicular to the burning surface by applying a magnetic field to orient the staples perpendicular to the burning surface as the propellant is cast. The propellant is then cured while the staples are oriented to retain the desired orientation.
Metal staples and flakes have been employed extensively in propellant compositions wherein the staple sizes and flake particle sizes and percentages have achieved improved burning rates without particular means for achieving controlled orientation of staples. Additionally, graphite fibers have been employed to achieve improved burning rates as disclosed in U.S. Pat. No. 4,072,546, issued to Richard Winer on Feb. 7, 1978.
Advantageous would be a method to achieve additional burning rate increase in a propellant composition containing metal staples and flakes wherein the effect to improve burning rate is achieved through the use of electrical field effects. This approach to increasing the burning rate would not require a change to the propellant ingredients or formulation which could result in undesired changes to a proven propellant composition.
Therefore an object of this invention is to provide a method of accelerating the burning rates of solid propellants containing metal staples, metal flakes, etc., through the use of electric field effects.
A further object of the invention is to provide a mechanism whereby the burning rate of a propellant which is below the required value can be adjusted to the correct value.
Still a further object of this invention is to provide a means for adjusting the ballistic characteristics of a solid propellant in an all-ready fully-processed propellant grain.
Additionally, another object of this invention is to provide a means of correcting for the anistropy of burning rate in propellants which contain metal staples, metal flakes, etc., where non-random orientation may occur at the motor wall and mandrel surface.